GE ML1600 - Manual (Page 60)

4–4 MULTILINK ML1600 ETHERNET COMMUNICATIONS SWITCH – INSTRUCTION MANUAL
FUNCTIONALITY CHAPTER 4: OPERATION
Note In half-duplex mode, the ML1600 implements a back-pressure algorithm on 10/100 Mb
ports for flow control. That is, the switch prevents frames from entering the device by
forcing a collision indication on the half-duplex ports that are receiving. This temporary
“collision” delay allows the available buffer space to improve as the switch catches up with
the traffic flow.
4.1.8 Power Budget Calculations with Fiber Media
Receiver sensitivity and transmitter power are the parameters necessary to compute the
power budget. To calculate the power budget of different fiber media installations using
MultiLink products, the following equations should be used:
(EQ 4.1)
where: OPB = optical power budget
P
T
= transmitter output power
P
R
= Receiver Sensitivity
The worst case OPB is as follows:
(EQ 4.2)
The worst-case distance is calculated as follows:
(EQ 4.3)
The cable loss in dB/km is defined in the following table:
The following data has been collected to provide guidance to network designers and
installers.
Table 4–1: Cable losses
Cable size Mode Cable loss
62.5 / 125 μm multi-mode 2.8 dB/km
50 / 125 μm multi-mode 2.8 dB/km
100 / 140 μm multi-mode 3.3 dB/km
9 / 125 μm single-mode 0.5 dB/km
0.4 dB/km (LXSC25)
0.25 dB/km (LXSC40)
0.2 dB/km (LXSC70)
OPB P
t min ( )
P
R min ( )
– =
OPB
worst
OPB 1dB (LED aging) – 1dB (insertion loss) – =
distance
worst
worst-case OPB (in dB)
cable loss (in dB/km)
-------------------------------------------------------- =
Table 4–2: Power budget values for various modules
Module Speed Mode fdx (hdx) λ Size P
T
P
R
OPB
worst
d
worst
OPB
typ
d
typical
A1, A5 10 Mb FL multi 2 (2) km 850 nm 62.5/125 μm
100/140 μm
50/125 μm
-15.0 dB
-9.5 dB
-19.5 dB
-31 dB
-31 dB
-31 dB
14 dB
19.5 dB
19.5 dB
5.0 km
5.9 km
3.4 km
17 dB
23.5 dB
13.2 dB
6.0 km
7.0 km
4.8 km
A2, A3, A6 100 Mb FX multi 2 (0.4) km 1300 nm 62.5/125 μm
50/125 μm
-20 dB-
23.5 dB
-31 dB
-31 dB
9.0 dB
5.5 dB
3.0 km
2.0 km
14 dB
12 dB
5.0 km
4.0 km
A7, A8 100 Mb FX single 18+ (0.4) km 1300 nm 9/125 μm -15 dB -31 dB 14 dB 28 km 17.5 dB 35 km
AA, AB 100 Mb FX multi 2 (0.4) km 1310 nm 62.5/125 μm -19 dB -31 dB 12 dB 4.0 km 16 dB 5.7 km
AC, AD, AE 100 Mb FX single 15+ km 1310 nm 9/125 μm -15 dB -28 dB 11 dB 22 km -- --
AF 10 Mb FL multi 2 (2) km 850 nm 62.5/125 μm
100/140 μm
50/125 μm
-15.0 dB
-9.5 dB
-19.5 dB
-31 dB
-31 dB
-31 dB
14 dB
19.5 dB
9.5 dB
5.0 km
5.9 km
3.4 km
17 dB
23.5 dB
13.5 dB
6.0 km
7.0 km
4.8 km